Inverters

Many different types of inverter can be used in a solar power system. There are dedicated inverters for solar power available, but what's important is that the correct inverter is used for the job it has to do. This job is converting a certain amount of power from low voltage DC to 230 Volts AC to power mains appliances. The right inverter will deliver enough power but will be no bigger than necessary, and will have the right output waveform.

How it Works

Most people are familiar with the idea of a transformer. A transformer is a device that converts one voltage into another, so why do we need an inverter? Well the problem with a transformer is that it can only work with alternating current or AC. The power from the battery in a solar power system is direct current or DC.

Roughly, what an inverter does is to turn this DC into AC by rapid transistorised switching, and then use a transformer to convert it to the correct AC voltage. Depending on how this is done, the result can be either a sine wave like the mains or a modified sine wave which approximates to the mains.

Inverter Types

Inverters come in many different sizes. The smallest and cheapest, like the one shown, are basic modified sine wave devices designed to be plugged into a lighter socket. The top end of the market provides inverters rated at many kilowatts, with a sine wave output and additional features such as generator control. As a rule, a smaller system will use a small inverter to power exceptional loads, whereas a larger system may have everything powered from the inverter.
The choice of waveform is dependent on the loads; a modified sine wave inverter is likely to be cheaper and more efficient, so a sine wave inverter would be chosen only if mains-quality power is specifically needed, for example for a high-quality sound system.

Synchronous Inverters

A different sort of inverter is used in grid-connected systems. This is known as a synchronous inverter. It is called this because it synchronises its output with the incoming mains power, so that power can be fed back into the grid. Synchronous inverters also include comprehensive safety features to protect anybody working on the electricity cables. They must be approved by the electricity company for connection to their network.